One significant area of environmental concern affecting many urban areas of the United States and many other developed countries is the impact of storm water runoff on surface water quality. In the United States, since March 2003, the Clean Water Act National Pollution Discharge Elimination System (NPDES) Program requires communities to manage the quantity and quality of storm water runoff. Such storm water runoff may originate, for example, from parking lots, roads, building roofs, sidewalks, and other surfaces that contain many types of pollutants. Such surfaces are referred to herein as impervious surfaces. Storm water runoff may contain sediment and pollutants that have adverse impacts on downstream users of the water. For example, storm water runoff from the surface of a parking lot, street, and/or driveway may contain petroleum impurities, such as from oil leaks of vehicles parked at the lot and the parking lot surfacing material. The storm water runoff may also contain potentially harmful chemicals, such as ethylene glycol (anti-freeze), and particulates from various gravel, sand, litter, and tire rubber. Runoff from such surfaces, if left untreated, may find its way into streams, rivers, lakes, and/or groundwater supplies and have an adverse impact on users (including wildlife) of the water supplies. Accordingly, the NPDES requires communities to manage such runoff.
In order to comply with federal regulations, many municipalities and local government agencies are forming, or have formed, storm water utilities to address the increasing fiscal burden of meeting many of the water quality regulatory requirements. Many of these storm water utilities generate bills for property owners within the municipality based on the impervious surface area owned by the property owner. The generation of parcel maps and the determination of pervious/impervious surface area contained within each parcel can be a significant task for such storm water utilities. Such utilities generally have a limited budget, and thus limited resources available to accomplish these tasks. Furthermore, with continuing development, both in existing developed areas and new developments, maintaining a complete and up-to-date parcel map, along with the determination of pervious/impervious surfaces, is a continuing challenge for many communities.